• Journal of ILASS-Korea
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• v.15 no.1
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• pp.8-16
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• 2010

This paper present the diesel spray characteristics at different injection system parameters in a HSDI diesel engine. The spray characteristics was calculated by the coupled simulation of fuel injection system model and three-dimensional KIVA-3V code with TAB spray model. The relevant injection parameters are accumulator volume, control chamber initial volume, control orifice diameter, needle valve diameter and nozzle chamber initial volume, etc. Parametric investigation with respect to twelve relevant injection parameters showed that there was a significant advantage in varying control chamber initial volume, control chamber orifice diameter, and nozzle chamber orifice diameter with respect to effect the SMD and fuel injection speed. Consequently, in order to design the fuel injection system for spray characteristics, it seems reasonable to suppose to be optimized the fuel injection system.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.2
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• pp.39-45
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• 1988

The analytical model of an engine mount system with six degrees of freedom is identified using the modal parameters obtained from the experimental modal analysis. The structural parameters, mass moment of inertia of the engine block and stiffness of the rubber mounts, of the engine mount system are determined by using the condition that the estimated model parameters should satisfy the corresponding eigenvalue problem. The simulated modal parameters of the identified analytical model are in good agreement with the measured modal parameters.

• Tunnel and Underground Space
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• v.12 no.4
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• pp.268-276
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• 2002

In this study, a 3D coordinate measurement system equipped with a laser displacement meter for digitizing rock joint surface was established and the digitized data were used to calculate several roughness parameters. The parameters used in this study were micro avenge inclination $angle(i_{ave})$, average slope of joint $asperity(SL_{ ave})$, root mean square of $i-angle(i_{rms})$, standard deviation of height(SDH), standard deviation of $i-angle(SD_i)$, roughness profile $index(R_P)$, and fractal dimension(D). The relationships between the roughness parameters based on the digitzation of the surface profile were analyzed. Since the measured value varied according to the degree of reflection and the variation of colors at the measuring point, rock joint surface was painted in white to minimize the influence of the surface conditions. The comparison of the measured values and roughness parameters before and after painting revealed the better consequence from measurement on the painted surfaces. Also, effect of measuring interval was studied. As measured interval was increased, roughness parameters were exponentially decreased. The incremental sequence of degree of decrease was $SDH\; i_{ave},\; i_{rms},\; SD_i,\;and\; R_ p-1$. As a result of comparison of parameters from pin-type measurement system and laser type measurement system, all value of parameters were higher when laser-type measurement system was used, except SDH.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.6
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• pp.915-923
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• 2008

This paper focuses on optimal tuning of nonlinear parameters of a dual-input power system stabilizer(dual-input PSS), which can improve the system damping performance immediately following a large disturbance. Until recently, various PSS models have developed to bring stability and reliability to power systems, and some of these models are used in industry applications. However, due to non-smooth nonlinearities from the interaction between linear parameters(gains and time constants of linear controllers) and nonlinear parameters(saturation output limits), the output limit parameters cannot be determined by the conventional tuning methods based on linear analysis. Only ad hoc tuning procedures('trial and error' approach) have been used. Therefore, the steepest descent method is applied to implement the optimal tuning of the nonlinear parameters of the dual-input PSS. The gradient required in this optimization technique can be computed from trajectory sensitivities in hybrid system modeling with the differential-algebraic-impulsive-switched(DAIS) structure. The optimal output limits of the dual-input PSS are evaluated by time-domain simulation in both a single machine infinite bus(SMIB) system and a multi-machine power system in comparison with those of a single-input PSS.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.519-522
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• 2006

Accurate modeling of a dynamic system from experimental data is the bases for the model updating or heath monitoring of the system. Modal analysis or modal test is a routine process to get the modal parameters of a dynamic system. The modal parameters include the natural frequencies, damping ratios and mode shapes. This paper presents a new method that can derive the equations of motion for a dynamic system from the modal parameters obtained by the modal analysis or modal test. The present method based on the relation between the eigenvalues and eigenvectors of the state space equation derives the mass, damping and stiffness matrices of the system. The modeling of a cantilevered beam from modal parameters is an example to prove the efficiency and accuracy of the present method. Using the lateral displacements only, not the rotations, gives limited information for the system. The numerical verification up to now gives reasonable results and the verification with the test data is scheduled.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.71-75
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• 1994

This paper presents a method of optimal design of an automatic transfer system which is controlled by the electro-pneumatic servo scheme. The electro-pneumatic automatic transfer system can move parts to desired points or displace defective parts. The dynamic performance of the system can be examined by observing the behavior of the output. The output of the servo control system is the motion of the cylinder, pneumatic actuator. The dynamic performance of the cylinder is governed by the parameters of the components of the entire system. The optimal design can be accomplished by selecting of the parameters such that the desired dynamic performance of the cylinder is obtained. The optimal set of parameters might be obtained through the repeated simulations. Repeated simulations, however, is not effective to determine the optimal set of parameters since the set of parameters is large. This paper presents modeling, application of an optimization method, and the numerical results. The optimization algorithm utilizes the concept of the conjugate gradient method. The results show that the suggested optimization scheme can render faster convergence of iteration compared to other method based on an algebraic optimization method and can reduce the design efforts.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.61-63
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• 1999

This paper presents an efficient method for analysis of magnetodynamic system using frequency-dependent parameters. In equivalent electric circuit of linear magnetodynamic system, parameters of inductance and resistance are not constant since they vary with its driving frequency. Once frequency-dependent parameters of equivalent electric circuit for a given system are extracted, they can be used to analyze various characteristics of system. We use the Fourier transform, the high-order sensitivity method and Taylor series in order to efficiently extract the frequency-dependent parameters of magnetodynamic system. The proposed algorithm is applied to an induction heating system to validate its numerical efficiency.

• Solar Energy
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• v.18 no.4
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• pp.59-66
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• 1998

It was compared with experimental data to verify TRNSYS Model of the thermosyphon hot water system and the various simulations were conducted to optimize the component parameters of the system. To obtain consistent simulation results the system model, which could accurately describ the thermal storage tank temperature stratification and the friction head for mass flow rate, was used. The optimization of collector parameters(collector aspect ratio, riser numbers per header unit length), thermal storage tank parameters(ratio of tank length to tank diameter, heat exchanger type), system parameters(ratio of tank volume to collector area) was simulated by TRNSYS program. The simulation results indicate that the system performance is more effected by collector aspect ratio and the ratio of tank volume to collector area than the othor parameters.

• Structural Engineering and Mechanics
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• v.70 no.1
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• pp.81-96
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• 2019

In this paper, a hybrid uncertain model is applied to system reliability based design optimization (RBDO) of trusses. All random variables are described by random distributions but some key distribution parameters of them which lack information are defined by variation intervals. For system RBDO of trusses, the first order reliability method, as well as monotonicity analysis and the branch and bound method, are utilized to determine the system failure probability; and Improved (${\mu}+{\lambda}$) constrained differential evolution (ICDE) is employed for the optimization process. System reliability assessment of several numerical examples and system RBDO of different truss structures are proposed to verify our results. Moreover, the effect of different classes of interval distribution parameters on the optimum weight of the structure and the reliability index are also investigated. The results indicate that the weight of the structure is increased by increasing the uncertainty level. Moreover, it is shown that for a certain random variable, the optimum weight is more increased by the translation interval parameters than the rotation ones.

• Structural Engineering and Mechanics
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• v.7 no.4
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• pp.387-400
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• 1999

Damage detection in civil engineering structures using the change in dynamic system parameters has gained a lot of scientific interest during the last decade. By repeating a dynamic test on a structure after a certain time of use, the change in modal parameters can be used to quantify and qualify damages. To be able to use the modal parameters confidentially for damage evaluation, the effect of other parameters such as excitation type, ambient conditions,... should be considered. In this paper, the influence of excitation type on the dynamic system parameters of a highway prestressed concrete bridge is investigated. The bridge, B13, lies between the villages Vilvoorde and Melsbroek and crosses the highway E19 between Brussels and Antwerpen in Belgium. A drop weight and ambient vibration are used to excite the bridge and the response at selected points is recorded. A finite element model is constructed to support and verify the dynamic measurements. It is found that the difference between the natural frequencies measured using impact weight and ambient vibration is in general less than 1%.